A cooling fan in an air-cooled engine is driven by a crankshaft to send cooling air to a cylinder head and a cylinder block, whereby they are forcibly cooled. This type of air-cooled engine is disclosed in Japanese Examined Utility Model Application No. 58-19293.
The air-cooled engine in Japanese Examined Utility Model Application No. 58-19293 comprises an engine main body, a cooling fan, a recoil starter, and a fan cover for covering the cooling fan and the recoil starter. The recoil starter is manually operated to start up the engine main body.
The fan cover is a roughly cup-shaped member that conducts cooling air sent from the cooling fan to the cylinder head and the cylinder block.
The fan cover is often made from a resinous material in order to achieve a weight reduction and improved productivity. A resinous fan cover is mounted on the crank case of an engine with stud bolts or other such fastening members. For example, the top board of the fan cover is mounted on the distal ends of the stud bolts provided to the crank case at positions on the inner side of the fan cover.
However, a guiding duct for guiding cooling air sent from the cooling fan to the cylinder head and the cylinder block is formed inside the fan cover. When the stud bolts are disposed in this guiding duct, measures must be taken to reduce (1) the wind roar resulting from the cooling air striking the stud bolts, and (2) the transmission resistance resulting from the stud bolts hindering the flow of cooling air. “Wind roar” refers to the loud noise caused by friction between the cooling air and the stud bolts or other such obstacles.
In view of this, there is a need for techniques whereby the occurrence of wind roar can be prevented when cooling air flows through the fan cover, and whereby cooling air can be adequately guided by the fan cover.